One by one, the small banks that had blocked approval of the Chrysler Corp. financial aid plan gave in yesterday, bowing to personal appeals from Treasury Secretary G. William Miller and local Chrysler suppliers in their hometowns -- and, in one case, to an anonymous bomb threat.

By late yesterday the entire group of 400 U.S. and foreign banks appeared to have agreed to accept delayed payment on $4.4 billion in Chrysler debt while the company tries to recover. The banks' agreement appeared to clear the way for Chrysler to pick up the first installment of the $1.5 billion in loans guaranteed by the federal government.

Among themselves, the banks have insisted that there would be no agreement unless every one of Chrysler's creditors signed on.

The last holdout bank was the Deutsche Genossenschaftsbank of Frankfurt, which recently seized $8.6 million in Chrysler funds as security for money it is owed by the auto company.

Late yesterday, however, Chrysler officials announced that agreement in principle had been reached with the West German bank in eleventh-hour negotiations. Both Treasury Department and company officials were confident throughout the day yesterday that the final opposition would collapse, permitting Chrysler to receive the first $500 million installment on the government-guaranteed loans approved by Congress in December.

The final holdout, like the American National Bank & Trust Co. in Rockford, Ill., found itself standing almost alone in the face of tremendous pressure to accept the Chrysler aid plan.

David W. Knapp, president of the Rockford bank, said it had reversed its position late Thursday out of concern for the impact of a Chrysler bankruptcy on the economy, and for the safety of its employes. He said the bank had received an anonymous bomb threat over the telephone Thursday morning.

"There was a lot of pressure in a lot of different ways," a tired, deflated Knapp said yesterday. The bank had opposed the Chrysler plan, arguing that the company should pay its $525,000 debt or face the consequences. Bank officials doubted that the $1.5 billion in federally guaranteed loans would save the struggling automaker.

Chrysler's suppliers in the Rockford area had besieged the bank with appeals, and local United Auto Workers officials from the nearby Belvidere, Ill., Chrysler plant, had called on their members to boycott the bank.

"First, we sense a division taking place within the community, a community involved with the Chrysler Corp. in many ways," Knapp said. "Secondly, we are concerned for the safety of our employes and their families."

Knapp said he had received a call Thursday from Miller, urging the bank to reconsider its position. The Treasury secretary, chairman of the Chrysler Loan Guarantee Board, spent a busy day on the telephone.

Another call went to Donelly McDonald, chairman of People's Trust Bank of Fort Wayne, Ind., another of the holdouts that gave in late Thursday.

Dieter Heren, the bank's vice president for corporate loans, had said earlier the Chrysler situation would be treated "strictly as a business decision. We haven't wavered from that position."

The bank was holding on to about $300,000 in Chrysler funds as security against an outstanding $1 million obligation owed the bank by the company and had sued Chrysler for the remaining $716,500. Under the Chrysler loan agreement, the bank cannot keep a direct hold on even that small piece of the auto company. First claim on Chrysler's assets in the case of a default will go to the investors who buy the new $10,000 debentures to be backed by the government's loan guarantee, assuming the plan finally is confirmed.

Heren said yesterday that Miller was sympathetic with the bank's position, but stressed the impact on the entire economy if the Chrysler plan failed. "It was a straightforward call. There was no pressure," he said.

The bank's directors also heard from the local Dana Corp., which supplies axles for Chrysler's Dodge division. Chrysler has suspended payments to all its suppliers this month to conserve its cash, confronting them with an immediate loss of more than $150 million if Chrysler were to fail this month.

"We had to reconsider our position," said Heren.

Chrysler and its allies had less leverage in dealing with the holdout German bank, but there are some pressure points there, too, said sources close to the Chrysler negotiations.

The $8 million seized by the bank was being transferred to Chrysler from Volkswagen, following the sale of Chrysler property in Argentina to the West German auto company, sources said, and Volkswagen had been expected to object strenuously.